A. Field of the Invention
The present invention relates to an endoscope having an elastic actuator driven by supplying or discharging a fluid.
B. Description of the Prior Art
A typical industrial endoscope is used to check an internal portion which cannot be directly viewed from the outside by an operator, e.g., an engine of an aircraft or an interior of a narrow tube. Such an industrial endoscope has illumination and observation optical systems at its distal end portion of an insertion portion. Therefore, even if a portion to be observed is located at a deep position of a bent path, the distal end portion can be guided to a position close to the portion to be observed.
Japanese Patent Disclosure (Kokai) No. 59-146636 discloses a typical industrial endoscope. This endoscope has an insertion portion incorporating illumination and observation optical fiber bundles and a distal end constitution portion mounted at the distal end of the insertion portion. A cylinder and a piston are provided in the insertion portion and move relative to each other by a pressure of a fluid supplied from the outside. A joint member of the insertion portion is bent by a relative motion of the cylinder and the piston, thereby bending the insertion portion.
Japanese Patent Disclosure (Kokai) No. 61-122834 discloses a typical endoscope to be inserted into a human body to observe a diseased part or the like. An insertion portion of this endoscope incorporates illumination and observation optical fiber bundles and a plurality of operation wires. One end of each operation wire is connected to a distal end constitution portion, and the other end thereof is connected to an angle knob provided to an operation portion. By pushing/pulling the operation wires by the angle knob, a bending portion of the insertion portion can be bent.
However, an endoscope having a cylinder and a piston driven by a pressure of a fluid in its insertion portion has a complicated arrangement and a heavy weight and requires a high fluid pressure to drive the piston inside the cylinder. In addition, since a drive unit of the insertion portion does not have elasticity, the insertion portion may cause damage to a peripheral unit when it is brought into contact with the unit.
In an endoscope in which an insertion portion is relatively long and angle operation wires are incorporated in the insertion portion, friction between the angle operation wires and wire guides is increased. Therefore, a large power is required to operate an angle knob.
Another typical example of an endoscope is an endoscope having an observation optical system, in which an observation field of the endoscope is changed or focus adjustment of the observation optical system is performed by operating operation wires inserted in a flexible tube portion and a bending tube portion of an insertion portion. However, in this endoscope, since a large space for housing the operation wires so that they can move forward and backward must be formed in the insertion portion, an outer diameter of the insertion portion is increased. In addition, friction between the operation wires and wire guides prevents a correct operation, and expansion of the operation wires degrades accuracy of focus adjustment.